1. Field of the Invention
This invention relates to a method for forming chenille yarns and the chenille yarns produced thereby.
2. Description of the Prior Art
Chenille yarn is a specialty yarn typically used in upholstery and decorative fringe applications. A chenille yarn includes a central portion, or core, from which short pile strands protrude.
Chenille yarn is typically formed on a yarn manufacturing device that co-twists two or more continuous yarns to form a core. Twisting the core yarns provides strength to the resulting chenille yarn. The pile, which is formed of discontinuous fibers, is gripped between and protrudes transversely from around the core yarns.
U.S. Pat. No. 5,496,508 (Tung et al.) is exemplary of the typical process for the formation of a high-bulk chenille yarn. A binding thread is formed by air texturing a polyethylene yarn with a binder yarn. A chenille yarn is formed by twisting together a pair of the binding threads so as to engage sheared lengths of pile yarn therebetween. During finishing the polyethylene component of the chenille yarns is melted to bond the pile yarns to the binding threads.
Chenille yarns may also be formed by slitting the fill threads of a woven fabric intermediate the longitudinally extending warp threads of the fabric to form narrow ribbons. Thereafter, two or more of the resulting ribbons are twisted together.
U.S. Pat. No. 3,715,878 (Kim) discloses a process for making chenille yarn in which longitudinal warp threads are provided both above and below web of fill threads. The warp threads are bonded to the fill threads and slit between the warp threads to form the chenille yarn.
U.S. Pat. No. 5,498,459 (Mokhtar et al.) discloses a tuft-string structure having pile yarn bundles bonded to a central support strand. The pile yarn bundles extend in only one direction from the central support strand such that, when attached to a backing, a pile surface structure (carpet) is formed.
Japan Published Application 4-352,840 discloses a process for forming a chenille yarn from a knit fabric. A plurality of foundation yarns is formed. Each foundation yarn has a longitudinally extending core thread formed as a chain stitch. Transversely extending filaments link together adjacent foundation yarns. The transversely extending filaments are cut, forming the chenille yarn. The use of a heat-activated binder material is avoided as this is seen to cause the chenille yarn to have a stiff feel. The product relies on the tightness of the chain stitch to prevent pile pull-out and therefore, durability is limited.
The process disclosed in U.S. Pat. Nos. 3,168,883 and 3,837,943 (both to Ploch et al.) uses composite binder stitching threads and shrinkable yarns to post-tighten chain stitch loops and form durable velours or stitchbonded fabrics using a backing. The backing is not an adhesive layer that can be used as the binder in a chenille.
In view of the foregoing it is believed advantageous to provide a low cost process for forming chenille yarn that both very durable, and at the same time, soft, flexible and, preferably, stretchable. Multiple color capability, multiple fiber capability in pile and long pile is also believed desirable.
The present invention is directed to a method of producing a chenille yarn by forming a warp knit fabric in which a web of transversely extending underlaps connects adjacent overlaps of longitudinally extending stitches. The stitch overlaps are arranged in adjacent longitudinally extending wales. A binder material extends with the overlaps along the wales.
The binder material may be introduced into the knit fabric in a variety of ways. A strand of binder may be laid into the stitches or may be inserted transversely into the stitches. Alternatively, the binder may be provided in sheet form with the stitches penetrating into the sheet. Binder can also be introduced using a composite low melting temperature/high melting temperature thread as the stitching thread.
The transversely extending underlaps are slit between adjacent wales thereby to define a plurality of precursor chenille yarns, each precursor chenille yarn including a wale of stitch overlaps and binder surrounded by an array of slit transverse underlaps. Either before or after slitting either the knit fabric or the precursor chenille yarns (as the case may be) is(are) heated to activate the binder. The binder material has a tendency to contract under heating into a continuous, longitudinally extending, elongate, irregular-shaped stripe, thus causing the fabric or the precursor chenille yarn to shrink or to contract longitudinally. Accordingly, in accordance with this invention, either during or after heating a tensile force is applied to the fabric or the yarn. The tensile force either prevents the formation of such a continuous stripe of binder chain within the core or breaks the continuity of the stripe of binder into discrete beads of binder material, thereby to form a finished chenille yarn. The core of the finished chenille yarn is defined by the overlaps of the stitches and the pile of the finished chenille yarn is defined by the slit transverse underlaps, with the pile of the finished chenille yarn being held to the core by one or more discrete bead(s) of binder.
The method of the present invention is believed to provide an efficient way to make chenille yarn in which the pile yarn is secured to the core by the beads of binder material. The tendency of the binder to form continuous, longitudinally extending, elongate, irregular-shaped stripe is countered by the application of the tensile force either during or after heating, as the case may be.